This invention relates to a rotary damper means for braking both opening and closing motions of various closing devices such as cassette lids and doors, and more particularly to a rotary damper means for braking and absorbing such opening and closing motions of lids and doors by the combined action of a coil spring and viscous oil.
Various rotary dampers are used, for example, for the purpose of braking sudden spring-action opening motions of cassette lids in cassette tape recorders and video cassette recorders. The rotary dampers of this type include frictional rotary dampers adapted to brake the opening and closing motions by the frictional contact of a built-in rotary member and oil type rotary dampers which provide their braking function by keeping a similar rotary member in a bath of highly viscous oil such as silicone oil (U.S. Pat. No. 4,342,135).
All such conventional dampers comprise numerous component parts, require much time and labor for assembly, occupy large spaces, and are high in cost.
In Japanese Patent Application No. SHO 54(1983)-55429 (filed on Apr. 15, 1983), therefore, the inventor proposed a rotary damper means using a spring such as a coil spring which is capable of being wound from one end thereof, such that, when a cassette lid is closed from its open state by the hand, for example, the coil spring is wound from one end thereof by the fore of the pressure and consequently caused to generate gradual braking force and prevent the cassette lid from being violenntly closed with a bang and, just before becoming completely wound, stopped in place by an engaging member and prevented from unwinding itself to keep the cassette lid in a closed position and, when the cassette lid is subsequently opened from its closed state, the coil spring is released from the engaging member and enabled to unwind itself in a braked condition and gently open the cassette lid.
Use of this rotary damper means in an opening-closing device offers an advantage that the opening and closing motions of the device can be braked by simply combining a spring serving to draw the opening-closing device constantly toward its opened position, a locking mechanism serving to lock the device in its closed position, means incorporated in the damper means and adapted to release the locking mechanism, the damper means interposed between the opening-closing device and the main body using this device, and a toothed wheel or sector gear possessing teeth fitting the teeth of the toothed wheel in the damper device. In spite of this advantage, the combination still uses numerous component parts, requires much time and labor for assembly, and therefore is high in cost.
In the circumstances, there is growing demand for damper means which permits a locking mechanism and means for its release to be disposed between an opening-closing device and a main body using this device, incorporates a coil spring in itself to brake both opening and closing motions of the opening-closing device and, at the same time, relies solely on the force of the coil spring to open the opening-closing device.